1. Field of the Invention
The present invention relates to an image processing device, method, and program, and an objective function and, more specifically, to an image processing device, method, and program, and an objective function suitable for use with three-dimensional (3D) body tracking for modeling, based on images being results of sequential imaging of an object such as human being in motion, the motion of the object using a 3D body configured by a plurality of parts.
2. Description of the Related Art
With 3D body tracking, as exemplarily shown in FIGS. 1A and 1B, in frame images F0 and F1 being results of time-sequential imaging, an object in the frame image F0 being a reference frame image is divided into several parts, e.g., part of head, part of torso, part of arm from shoulder to elbow, part of arm from elbow to finger tip, part of leg from lap to knee, part of leg from knee to toe, and others. Each of these parts is made three dimensional, and the resulting image is a 3D body image B0. In such a 3D body image B0, the motion of each of the parts is tracked based on the frame image F1, thereby generating a 3D body image B1 corresponding to the frame image F1.
The concern here is that, at the time of tracking the motion of each of the parts, if the parts are individually subjected to such motion tracking, the parts that are supposed to be connected to each other by joints may be separated, e.g., refer to a 3D body image B′1 of FIG. 1D. To prevent occurrence of such a problem, motion tracking is required to be performed in accordance with such requirements as “a part is being tangent to another at a predetermined joint point”. Hereinafter, such requirements are referred to as joint constraints.
To meet such requirements, various many methods of tracking with joint constraints have been proposed, e.g., Non-Patent Document 1 (D. Demirdjian, T. Ko and T. Darrell. “Constraining Human Body Tracking”. Proceedings of ICCV, vol. 2, pp. 1071, 2003), Non-Patent Document 2 (Christoph Bregler, Jitendra Malik and Katherine Pullen. “Twist Based Acquisition and Tracking of Animal and Human Kinematics”. IJCV, vol. 56, no. 3, pp. 179-194, 2004), Non-Patent Document 3 (Steffen Knoop, Stefan Vacek, and Rudiger Dillmann. “Modeling Joint Constraints for an Articulated 3D Human Body Model with Artificial Correspondences in ICP”. Proceedings of Humanoids, pp. 74-79, 2005), and Non-Patent Document 4 (Ivana Mikic, Mohan Trivedi, Edward Hunter and Pamela Cosman. “Human Body Model Acquisition and Tracking Using Voxel Data”. IJCV, vol. 53, no. 3, pp. 199-223, 2003).